1. Field of the Invention
This invention relates to apparatus for affording access to computer software only by authorized persons, and more particularly to apparatus physically independent of the computer equipment but capable of executing an algorithm that can also be executed by the computer equipment to afford access.
2. Description of the Prior Art
Computer software, whether in the form of an operating system program or an application program, is typically stored in media that afford convenient access to a user. Exemplifying such media are main computer memory as well as peripherals such as magnetic disks, magnetic diskettes or magnetic tape. Software on such media requires substantial time and money to develop and it is desired in most cases to limit access to the software to only certain persons.
Numerous techniques for limiting access to computer software are practiced. In multiuser systems it is typical for each user to have an identification code and/or a password which the user must enter before gaining access to the system. Security of the software can be compromised when an authorized user reveals his or her identification code and/or password to unauthorized persons or the access code is discovered by a persistent hacker.
Another technique employed, particularly with respect to application software that is provided on magnetic diskettes, is to encode on the diskette a protective routine that causes the operating system to disable any copying facilities within it. This technique has had only moderate success in preventing unauthorized use or unauthorized copying because programs for disabling such protective routines are widely available.
Although the above described techniques and the copyright laws have impeded unauthorized use and/or copying of computer software, the creators of software continue to experience losses as a result of the activities of unprincipled copiers. This has impeded the creation of software and the allocation of resources necessary to the creation of software.